2024 Cambridge IGCSE Environmental Management (0680) Practice Paper with Answers

(a) Loose sediment is highly susceptible to liquefaction, where seismic shaking increases water pressure in the pore spaces, causing the soil to behave like a liquid. This causes building foundations to sink or tip. Solid bedrock like granite remains stable and does not liquefy. Additionally, seismic waves slow down and increase in amplitude (height) when they transition from hard rock to soft sediment, leading to more violent ground shaking in Town A.

(b) Effective engineering strategies include: 1. Base isolation systems (rubber and steel pads under foundations) that decouple the building from ground movement. 2. Cross-bracing and shear walls to provide lateral stability and prevent twisting. 3. Tuned mass dampers (heavy weights) near the top of skyscrapers that swing in opposition to seismic sway. 4. Flexible steel frames instead of brittle concrete or unreinforced brick.

(c) The disparity in death tolls is largely socioeconomic: LICs struggle with rapid, unregulated urbanization leading to poor-quality housing with weak construction standards. Emergency response plans, search-and-rescue equipment, and healthcare infrastructure are often underfunded, meaning survivors cannot be rescued or treated in time. In contrast, HICs invest heavily in earthquake-safe architecture, early warning systems, regular public drills, and heavily equipped emergency services.

(a) Max 3 marks:
- 1 mark for identifying/describing liquefaction (loose sand acts like a liquid under stress).
- 1 mark for explaining that liquefaction leads to loss of bearing capacity / structural collapse of foundations.
- 1 mark for explaining that seismic waves are amplified/strengthened in soft sediments compared to hard bedrock.

(b) Max 3 marks:
- 1 mark for each valid engineering method described (up to 3):
* Base isolators / rubber dampers to absorb shock / separate foundation from movement.
* Cross-bracing / steel reinforcement / shear walls to resist lateral forces.
* Tuned mass dampers to counteract building sway.
* Flexible materials (e.g., steel frames rather than brittle concrete).

(c) Max 4 marks:
- 1 mark for weak building codes / lack of enforcement of construction standards.
- 1 mark for poorly funded / equipped emergency response / medical services.
- 1 mark for lack of public education / warning systems / evacuation plans.
- 1 mark for high population density in informal settlements (slums) built on high-risk slopes/areas.

(a) Rising magma forces its way through the Earth's crust, cracking the surrounding rock. This fracturing generates small, localized seismic tremors called micro-earthquakes. As magma nears the surface, the confining pressure decreases, allowing volatile gases dissolved in the magma—especially sulfur dioxide (\(SO_2\))—to escape and vent into the atmosphere. An exponential increase in both seismic frequency and gas output provides strong physical evidence that magma is highly active and nearing the surface, signaling an imminent eruption.

(b) Volcanic regions offer substantial economic benefits: 1. Volcanic ash and rocks weather rapidly to produce extremely fertile soils high in minerals, boosting agricultural yields and crop values. 2. Geothermal heat can be tapped to generate cheap, clean electricity and support district heating. 3. Volcanic landscapes, hot springs, and dramatic terrain attract massive numbers of tourists, supporting local businesses.

(c) Residents often ignore evacuations due to: 1. Financial constraints—they cannot afford the cost of transport, temporary housing, or starting over. 2. Loss of livelihood—leaving means abandoning crops, livestock, or business premises to potential theft or destruction. 3. Cultural/ancestral ties—deep emotional connections to their homeland. 4. Overconfidence/complacency—if past warnings did not lead to major eruptions, people may assume current warnings are false alarms.

(a) Max 4 marks:
- 1 mark for explaining that magma movement causes rock fracturing, leading to micro-earthquakes.
- 1 mark for linking the rising frequency of earthquakes directly to magma moving closer to the surface.
- 1 mark for explaining that depressurization of rising magma releases trapped gases like \(SO_2\).
- 1 mark for concluding that sharp increases in both parameters show magma is ascending and highly active.

(b) Max 2 marks:
- 1 mark for each valid economic benefit described (up to 2):
* Fertile volcanic soils (enrich agricultural production).
* Geothermal energy potential (electricity generation / heating).
* Tourism opportunities (jobs, hotels, guided tours).
* Mining of valuable minerals/sulfur/pumice.

(c) Max 4 marks:
- 1 mark for each valid reason (up to 4):
* Cannot afford costs of moving / low income.
* Reluctance to leave behind livestock, crops, or assets.
* Cultural, ancestral, or spiritual ties to the land.
* Optimism bias / complacency due to past false alarms.
* Distrust of authorities / scientists.
* No alternative housing or support provided by the state.

(a) (i) The overall trend is a continuous, rapid decline in cod catch from 480,000 tonnes in Year 1 to 48,000 tonnes in Year 10.
(ii) Formula: \(\text{Percentage Decrease} = \frac{\text{Initial Value} - \text{Final Value}}{\text{Initial Value}} \times 100\)
Calculation: \(\frac{480 - 48}{480} \times 100 = \frac{432}{480} \times 100 = 90\%\).

(b) (i) Closed seasons ban fishing during specific months, usually coinciding with the reproductive/spawning period. This protects breeding adults and allows them to lay eggs and replenish the stock.
(ii) Minimum mesh sizes regulate net spacing so that small, immature juvenile fish can swim through and escape. This ensures that fish are caught only after they have reached breeding age, maintaining the population structure.

(c) Enforcing international fishing quotas in open oceans is difficult because: 1. The high seas are vast, making regular patrols by fishery protection vessels prohibitively expensive and logistically challenging. 2. Many vessels register under 'flags of convenience' from countries that do not enforce international maritime laws, escaping jurisdiction and prosecution.

(a) (i) 1 mark for stating that the catch decreased / declined steadily over the 10 years.
(ii) 2 marks:
- 1 mark for showing correct working (e.g., \(\frac{480 - 48}{480}\) or 432).
- 1 mark for the correct answer of 90%.

(b) (i) Max 2 marks:
- 1 mark for identifying that closed seasons protect fish during their breeding/spawning period.
- 1 mark for explaining that this allows reproduction to occur successfully, raising recruitment/population levels.

(ii) Max 2 marks:
- 1 mark for stating that larger holes allow young/juvenile/undersized fish to escape.
- 1 mark for explaining that this allows them to reach sexual maturity and reproduce at least once before being caught.

(c) Max 2 marks (any two from):
- Oceans are vast / difficult to patrol / lack of surveillance assets.
- Flags of convenience allow fishers to bypass national laws.
- High financial costs of enforcement / lack of international funding.
- High value of illegal catch incentivizes illegal, unreported, and unregulated (IUU) fishing.

(a) Inside a marine reserve, populations are completely protected from fishing pressure. Fish grow larger and produce exponentially more eggs and larvae. As population density inside the reserve increases, resources become limited, prompting adult fish to migrate out. Additionally, currents carry fish larvae out of the reserve. This migration of adults and transport of larvae into adjacent fishable waters is the 'spillover effect', which replenishes fish stocks for commercial fisheries outside.

(b) (i) Carnivorous farmed species (like salmon) require large amounts of wild-caught fish transformed into fishmeal/fish oil, which depletes wild ocean populations. Cultivating herbivorous species (like tilapia or carp) allows farmers to use plant-based feeds, reducing the ecological footprint on marine food webs.
(ii) Recirculating Aquaculture Systems (RAS) filter and clean water within a closed-loop system. This minimizes clean water usage, captures waste solids (which can be used as fertilizer), and prevents contaminated effluent (rich in nitrogen and phosphorus) from polluting natural aquatic ecosystems.

(c) Unmanaged coastal shrimp farming often leads to: 1. Clearing of mangrove forests to build ponds, causing coastal erosion and loss of nursery habitats for wild marine species. 2. Discharge of highly concentrated organic wastes, causing eutrophication and oxygen depletion in nearby estuaries. 3. Prophylactic use of antibiotics and pesticides that contaminate wild species and foster antibiotic-resistant pathogens.

(a) Max 3 marks:
- 1 mark for stating that fish populations/sizes increase inside the protected reserve.
- 1 mark for explaining that fish/larvae migrate/spread out of the reserve into fished areas.
- 1 mark for linking this spillover to increased catch rates / sustainable yields for commercial fishers nearby.

(b) (i) Max 2 marks:
- 1 mark for explaining that herbivorous fish feed on plants/algae, removing the reliance on wild-caught fishmeal.
- 1 mark for linking this to reduced pressure on wild pelagic fish populations / ocean food webs.

(ii) Max 2 marks:
- 1 mark for explaining that RAS recycles water, reducing water extraction/use.
- 1 mark for explaining that it prevents the release of nutrients/pollutants/farmed species into the wild.

(c) Max 3 marks (any three from):
- Loss / clearing of mangrove ecosystems.
- Eutrophication / water pollution from excessive feed and organic waste.
- Spread of diseases / parasites to wild species.
- Contamination from antibiotics, hormones, or pesticides.
- Soil and groundwater salinization in adjacent agricultural land.

(a) (i) Natural gas is a fossil fuel (non-renewable) with lower emissions than coal (490 vs 820 \(g\text{ }CO_2e/kWh\)).
(ii) Life cycle assessment includes emissions from all stages: 1. Construction and drilling phase, which uses heavy machinery, steel, and concrete (all highly energy-intensive and carbon-emitting). 2. Small amounts of dissolved gases (like \(CO_2\) and \(H_2S\)) that are naturally trapped in underground rock reservoirs escape when geothermal steam is extracted.

(b) Geothermal power works as follows: 1. Water is pumped deep underground through injection wells into hot geological formations. 2. Earth's internal heat (from radioactive decay and magma) heats the water to high temperatures, converting it to high-pressure steam. 3. The steam rises up production wells and spins a turbine. 4. The spinning turbine drives a generator, which produces electricity. 5. The steam is condensed back to liquid water and returned to the ground.

(c) Expansion of geothermal power is limited by: 1. Geographic constraints—high-temperature geothermal resources are mainly found near active tectonic plate boundaries (e.g., Iceland, Ring of Fire). 2. Financial barriers—the initial drilling of exploratory and production wells is extremely expensive and carries financial risk if the heat source is insufficient. 3. Environmental/geological concerns—drilling and injecting pressurized water can trigger micro-seismic events (earthquakes).

(a) (i) 1 mark for Natural Gas.
(ii) Max 2 marks:
- 1 mark for identifying emissions from manufacturing, transport, and construction (concrete/steel/drilling machinery).
- 1 mark for noting that natural underground reservoirs contain trapped greenhouse gases (like \(CO_2\)) that are released during extraction.

(b) Max 4 marks:
- 1 mark for pumping water deep underground into hot rocks.
- 1 mark for explaining that the water is heated to form steam.
- 1 mark for stating that steam turns/spins a turbine.
- 1 mark for explaining that the turbine turns a generator to produce electricity.
- (Accept references to binary cycle plants where a secondary fluid with low boiling point is vaporized instead of steam).

(c) Max 3 marks (any three from):
- Restricted to specific tectonic areas / plate boundaries.
- High capital / exploration / drilling costs.
- Risk of triggering localized earthquakes / seismic activity.
- Geothermal reservoirs can cool down / deplete if extraction rate exceeds heat replenishment rate.
- Corrosive minerals in geothermal fluids can damage equipment, raising maintenance costs.

(a) (i) Terracing involves reshaping steep hillsides into a series of flat, step-like platforms. By reducing the gradient of the slope, it slows down the velocity of surface water runoff, which reduces its capacity to transport soil. It also increases water infiltration.
(ii) Contour ploughing means working the land along the contour lines of equal elevation. The resulting horizontal ridges and furrows act as miniature dams that trap rainwater, encouraging it to soak into the soil instead of forming rapid erosive channels running directly downslope.

(b) Organic fertilizers come from plant or animal waste (manure, compost), whereas inorganic fertilizers are synthetically produced salts (containing N, P, K). Organic fertilizers provide organic matter (humus) which acts as a natural binder, gluing sand, silt, and clay particles into stable structures called aggregates. This improves soil permeability and aeration. In contrast, inorganic fertilizers supply raw nutrients directly but do not enrich the organic content of the soil, leading to soil compaction, loss of crumb structure, and greater susceptibility to erosion over time.

(c) In large, flat fields, dry topsoil is highly vulnerable to wind erosion. Windbreaks—rows of trees or shrubs—reduce the kinetic energy of the wind by creating a physical barrier. This reduces the wind speed at ground level below the threshold velocity needed to lift and carry away soil particles, thereby keeping the nutrient-rich topsoil in place.

(a) (i) Max 2 marks:
- 1 mark for explaining that terracing reshapes steep slopes into flat steps/benches.
- 1 mark for explaining that this slows down surface runoff and increases water infiltration.

(ii) Max 2 marks:
- 1 mark for explaining that ploughing is done across the slope (along horizontal contours, not up-and-down).
- 1 mark for explaining that the furrows/ridges trap water and prevent it from carving channels / washing soil down.

(b) Max 4 marks:
- 1 mark for distinguishing origin: Organic is natural/animal/plant waste; inorganic is synthetically/chemically manufactured.
- 1 mark for identifying that organic fertilizer adds organic matter/humus (inorganic does not).
- 1 mark for explaining that organic matter binds soil particles into aggregates (improves structure/aeration).
- 1 mark for explaining that improved soil structure prevents compaction and increases water-holding capacity.

(c) Max 2 marks:
- 1 mark for explaining that trees/shrubs physically obstruct and slow down wind speed.
- 1 mark for stating that this prevents the wind from lifting, transporting, or blowing away loose topsoil.

(a) Unrestored open-cast mines pose serious hazards: 1. Physical instability: Steep, unsupported rock walls can collapse or landslide, posing danger to wildlife and people. 2. Acid Mine Drainage (AMD): Exposed iron sulfides in the rock react with rainwater and oxygen to produce sulfuric acid, which leaches heavy metals into surrounding soils and rivers, destroying aquatic life. 3. Air and soil degradation: High winds generate toxic dust from tailings, and barren landscapes suffer intense erosion due to lack of vegetation.

(b) Restoration follows structured phases: 1. Landform reconstruction (grading): The pit is filled with waste rock and reshaped to blend with the natural contours of the landscape, ensuring proper drainage. 2. Soil replacement: The original topsoil (which was stockpiled during the initial excavation) is laid back down over the graded waste rock. 3. Soil conditioning: Fertilizers or compost are added to replenish nutrients. 4. Revegetation: Fast-growing cover crops or native trees are planted to establish root networks that hold the soil in place and restore ecosystem function.

(c) Bioremediation—specifically phytoremediation—uses hyperaccumulating plants to extract heavy metal contaminants from soil. The roots absorb metals like lead or copper and store them in their above-ground plant tissue (leaves/stems). This removes the metals from the soil matrix. The plants are then harvested, gathered, and incinerated in controlled facilities, concentrating the toxic ash for secure disposal without destroying the soil structure.

(a) Max 3 marks:
- 1 mark for structural hazards (landslides, pit wall collapse, fall dangers).
- 1 mark for chemical/water pollution (acid mine drainage / toxic metals leaching into rivers).
- 1 mark for air pollution (dust from barren tailings/pits) / land degradation (loss of soil/habitats).

(b) Max 4 marks:
- 1 mark for backfilling/grading (filling the pit and leveling the land to avoid steep slopes).
- 1 mark for replacing the stockpiled topsoil over the surface.
- 1 mark for adding soil conditioners/fertilizers/organic matter to restore nutrients.
- 1 mark for planting vegetation/trees/cover crops to bind the soil and prevent erosion.

(c) Max 3 marks:
- 1 mark for stating that bioremediation uses living organisms (specifically plants/microbes) to absorb/break down pollutants.
- 1 mark for explaining that plants (hyperaccumulators) absorb heavy metals from soil through their roots.
- 1 mark for explaining that the plants are harvested and safely disposed of/incinerated, permanently removing the toxic metals from the site.

(a) (i) The minimum temperature required is \(26.5^\circ\text{C}\) (commonly rounded to \(27^\circ\text{C}\)).
(ii) Warm ocean water heats the air directly above it, causing extensive evaporation. As this moist air ascends into the atmosphere, the water vapor condenses to form clouds. Condensation releases latent heat energy. This heat warms the surrounding air, making it rise faster, lowering the atmospheric pressure further and drawing in more wind, driving the cycle that powers the cyclone.

(b) Wind hazards are aerodynamic forces that cause direct mechanical damage, such as uprooting trees, ripping roofs off buildings, and throwing debris. Storm surges, on the other hand, are hydrologic hazards. The combined force of low atmospheric pressure and driving winds pushes a wall of ocean water onto land, causing rapid, deep coastal flooding, which is responsible for the majority of drowning deaths and severe water damage to structures.

(c) To protect lives, countries can: 1. Build elevated, reinforced concrete cyclone shelters in low-lying areas. 2. Implement satellite-based early warning systems to track storm paths and broadcast timely evacuation orders. 3. Construct defensive structures like sea walls, dikes, and preserve natural barriers like mangrove forests. 4. Enforce strict building codes so structures can withstand high wind loads.

(a) (i) 1 mark for \(26.5^\circ\text{C}\) / \(27^\circ\text{C}\).
(ii) Max 2 marks:
- 1 mark for explaining that warm water drives high levels of evaporation / moisture in the air.
- 1 mark for explaining that condensation of this moisture releases latent heat, which acts as the energy source fueling the storm.

(b) Max 3 marks:
- 1 mark for explaining that wind hazards involve mechanical/structural damage (e.g., throwing debris, destroying power lines, collapsing buildings).
- 1 mark for explaining that storm surges involve seawater flooding/drowning (due to ocean water pushed inland).
- 1 mark for a clear contrast showing wind is atmospheric force while storm surge is water/flooding force.

(c) Max 4 marks:
- 1 mark for each valid preparation/management strategy (up to 4):
* Building elevated, storm-proof cyclone shelters.
* Installing early warning systems / tracking technology / public broadcasts.
* Educating the public on evacuation routes and emergency procedures.
* Constructing sea walls / coastal barriers / preserving mangrove forests.
* Enforcing wind-resistant building regulations / structural codes.
* Implementing land-use planning to restrict development on low-lying coasts.

(a) Convergent boundary (subduction zone). The denser Pacific plate subducts beneath the Indo-Australian plate into the mantle. High temperature and pressure melt the subducting plate, creating magma. Magma rises through cracks in the crust to erupt as lava, forming volcanoes. (b)(i) Increase = 8560 - 7450 = 1110 GWh. Percentage increase = (1110 / 7450) * 100 = 14.9%. (b)(ii) High-pressure steam extracted from underground reservoirs spins a turbine. The spinning turbine turns a generator, which generates electricity. (c) Advantages: 1. No greenhouse gas emissions (CO2) during operation, reducing contribution to climate change. 2. Constant, reliable renewable energy source. Disadvantages: 1. Release of toxic underground gases (e.g., hydrogen sulfide). 2. Potential land instability/subsidence. (d) Equipment: Digital temperature probes with automated data loggers and satellite telemetry. Variables to control: Depth of measurement (e.g., 2m deep), distance from shore, and the recording interval (e.g., hourly). Safety/Reliability: Use remote telemetry to avoid entering hazardous areas. Calibrate probes before deployment, use multiple probes at different spots to calculate a mean, and filter out anomalies. (e) 1. Strict building codes (base isolators, reinforced concrete, flexible gas joints). 2. Public drills and education (e.g., ShakeOut). 3. Land-use zoning to prevent building on active fault lines or liquefaction-prone soils.

Total: 26.6 marks. (a) 4 marks: 1 mark for convergent/subduction boundary; 3 marks for process (subduction, melting/magma creation, magma rising through crust). (b)(i) 3 marks: 1 mark for calculating increase (1110); 1 mark for correct formula; 1 mark for correct final value (14.9%). (b)(ii) 2 marks: 1 mark for steam turning turbine; 1 mark for turbine driving generator. (c) 4 marks: 1 mark for each of two advantages and 1 mark for each of two disadvantages. (d) 7 marks: 2 marks for equipment (probes, loggers, telemetry), 2 marks for controlled variables (depth, location), 3 marks for safety/reliability (remote data collection, multiple probes for mean, calibration). (e) 6.6 marks: 2.2 marks for each of three well-explained management strategies (building codes, public drills, land-use zoning).

(a) The EEZ gives New Zealand sole sovereign rights to control and conserve marine resources within 200 nautical miles of its shores. This allows the government to set catch limits, exclude foreign vessels, and enforce sustainable fishing practices without international interference. (b)(i) Positive correlation: as estimated snapper biomass increases, the TACC also increases. (b)(ii) A TACC ensures that the total harvest does not exceed the maximum sustainable yield. It prevents overfishing, allowing the remaining fish population to reproduce and replenish the stock. (c)(i) Minimum mesh sizes allow juvenile fish to escape through the nets. This ensures fish can grow to maturity and reproduce at least once before they are harvested, sustaining the population. (c)(ii) Closed seasons ban fishing during spawning periods. This protects breeding aggregations from heavy exploitation, increasing spawning success. (d) Use stratified random sampling: divide the coastal area into distance zones (e.g., 0-5 km, 5-15 km, 15-30 km, and >30 km from the coast). Partner with commercial fishers operating in these zones and randomly sample 100 snapper from their catch in each zone. Measure each fish's length using a standard measuring board. Repeat this process over multiple weeks to ensure representative data, and calculate the mean length for each zone. (e) 1. The vast size of the EEZ makes regular physical patrolling by patrol vessels extremely expensive. 2. High-grading or discarding smaller fish at sea is difficult to monitor without onboard observers or CCTV. 3. Illegal, unreported, and unregulated (IUU) fishing by dark vessels operating without transponders is hard to track.

Total: 26.6 marks. (a) 3 marks: 1 mark for exclusive rights/control; 1 mark for excluding foreign vessels; 1 mark for ability to enforce local laws. (b)(i) 2 marks: 1 mark for identifying positive correlation; 1 mark for citing data (biomass 18% to 41%, TACC 4500 to 6000 tonnes). (b)(ii) 3 marks: 1 mark for capping total catch; 1 mark for aligning harvest with reproductive rates; 1 mark for preventing stock collapse. (c)(i) 3 marks: 1 mark for letting juvenile/small fish escape; 1 mark for allowing them to reach breeding age/maturity; 1 mark for maintaining recruitment. (c)(ii) 3 marks: 1 mark for banning fishing during spawning; 1 mark for protecting breeding groups; 1 mark for maximizing reproduction success. (d) 6 marks: 1 mark for dividing into distance zones (stratified sampling); 1 mark for random sampling of catch; 1 mark for large sample size (e.g., 100 fish); 1 mark for standard measuring tool; 1 mark for repeating over time; 1 mark for calculating mean lengths. (e) 6.6 marks: 2.2 marks for each of three well-explained difficulties (geographic scale/patrol cost, high-grading/discarding detection, IUU dark vessels).

(a)(i) 1. Excess fertilizer is not absorbed by grass. 2. Rainfall washes soluble nitrates off the soil surface (runoff) or down into groundwater (leaching). 3. Nitrates enter nearby streams. 4. Rapid growth of algae creates an algal bloom. 5. This blocks sunlight, causing aquatic plants below to die. (a)(ii) 1. Depleted dissolved oxygen (hypoxia). 2. Rapid fish kills. (b)(i) Decrease = 8.4 - 0.8 = 7.6 mg/L. Percentage decrease = (7.6 / 8.4) * 100 = 90.5%. (b)(ii) x-axis: Monitoring Station / Width of buffer zone. y-axis: Mean nitrate concentration (mg/L). Interpretation: Buffer zones are highly effective at reducing nitrates in streams, and a wider buffer zone (15m) is much more effective than a narrow one (5m). (b)(iii) 1. The depth and position in the stream where water is sampled. 2. The livestock density and fertilizer application rates in the adjacent pastures. (c) 1. Precision fertilizer application based on soil nutrient testing. 2. Fencing off waterways to physically exclude livestock. 3. Rotational grazing to prevent soil erosion and compaction. (d) Soil Structure: Organic fertilizers add organic matter (humus), binding soil particles, improving structure, water-holding capacity, and aeration, whereas chemical fertilizers do not improve structure and can degrade soil biota. Leaching: Organic fertilizers release nutrients slowly as they decay, minimizing leaching risks. Chemical fertilizers are highly soluble and release nutrients instantly, leading to high leaching rates during rain.

Total: 26.6 marks. (a)(i) 5 marks: 1 mark for excess fertilizer remaining in soil; 1 mark for runoff/leaching into water; 1 mark for nutrient enrichment causing algal blooms; 1 mark for blocking sunlight; 1 mark for death of submerged plants. (a)(ii) 2 marks: 1 mark for each of two correct symptoms (algal bloom, hypoxia, fish death, odor). (b)(i) 3 marks: 1 mark for calculating decrease (7.6); 1 mark for formula; 1 mark for correct final value (90.5% or 90.48%). (b)(ii) 4 marks: 1 mark for correct x-axis variable; 1 mark for correct y-axis variable with units; 2 marks for explaining that buffers significantly reduce nitrates, with wider being more effective. (b)(iii) 2 marks: 1 mark for each of two correct controlled variables (sampling location, sampling time, test method, adjacent farming intensity). (c) 6 marks: 2 marks for each of three well-described practices (precision fertilization, waterway fencing, rotational grazing, effluent ponds). (d) 4.6 marks: 2.3 marks for comparing soil structure impacts (organic adds humus/improves structure vs chemical lacks structure benefits) and 2.3 marks for comparing leaching risk (organic slow release/low risk vs chemical high solubility/high risk).